Redwood 2x4's

Agreed, you can use redwood for mudsills and bottom plates, as it is decay resistant and insect resistant (source: IRC section 319). You're likely going to get some strange looks from most people for "wasting" good redwood that way.

Redwood 2x4's

I am using redwood because that is what I saw my dad using 10 years ago to finish his basement other than that there is no reason. For studs I am using some 2x4's that I get when I recieve a shipment of goods at work. The shipper nails the 8' boards to the floor of the trailer. I just pull the nails and put them in my truck to use on my basement. Most are straiter than you can get at HD. I figure I have saved the money on them to spend the money on the RW. The boards on the floor of the trailer are to hold the pallets steady. I am not stealing anything from my employer